Harper was born in Dayton, Ohio, on January 20th, 1964. He played for Kiser HS in Dayton, and went on to the University of Miami (Ohio). While a college player, Harper was a rebounding machine. Strangely, on the pro level, this facet of his game all but disappeared. Harper was a starter all four seasons at Miami of Ohio, averaging 25 points and 11 rebounds as a junior, and 24 points, 12 rebounds, and 4 assists as a senior. The Cavaliers took him with the eighth pick of the 1986 NBA Draft.

Harper was an instant star in Cleveland. As a rookie, in 1987 he averaged 22.9 points per game, along with 5 rebounds and 5 assists. He also led the league in turnovers, but seemed to be well on his way to stardom. An injury caused him to miss 25 games of the 1988 season, and dropped his scoring average to 15.4 ppg. In the middle of the 1990 season, he was traded to the Los Angeles Clippers for Reggie Williams, and one of the biggest busts in NBA history, Danny Ferry. Harper was finally healthy again and was on a pace to duplicate his excellent rookie season, when he suffered a serious knee injury that kept him out for the rest of the season and most of 1991 as well. At the time, Harper was averaging 22.8 points, 6 rebounds, and 5 assists.

Harper recovered to post three excellent seasons for the Clippers, averaging 18, 18, and 20 points, though he had lost some of his explosiveness and was forced to rely more on his jump shooting; Harper never had been, and never would be, an excellent jump shooter.

After the 1994 season, the Chicago Bulls were looking for a replacement for Michael Jordan, who was playing baseball at the time. They signed Harper to a five-year deal, expecting him to provide the scoring punch that the team had been missing.

However, Harper was slow to learn the triangle offense, and was so unproductive that he was benched by coach Phil Jackson midway through the season. Jordan returned to the team near the end of the season, further reducing Harper's minutes. He scored a then-career low of 7 ppg.

This began Harper's mid-career transition from a star on bad teams to a productive role player on championship teams. Despite his horrendous 1995 season, Phil Jackson named him as one of his starters for 1996. The Bulls did not use a point guard, as starters Jordan, Scottie Pippen, and Harper were all combo guards with enough passing ability between them to successfully run the triangle, also known as the triple post offense. Harper's job was to play tough defense and knock down open shots, and he proved to be a steadying influence on the court. The Bulls won championships in 1996, 1997, and 1998, before owner Jerry Reinsdorf broke up the team. Jordan retired, Pippen was traded, and Dennis Rodman became a full-time flake. Only Harper and Toni Kukoc remained.

Harper attempted to carry more of the scoring load in the 1999 season, and did average 11 points, but shot an awful 38 percent from the floor. Harper's contract expired at the end of the season, and he followed coach Jackson to the Lakers, where he was assembling another championship squad around Shaquille O'Neal and Kobe Bryant. Harper was brought in to fill the exact same role he had filled as a Chicago Bull, with the exact same results. Harper would get two more rings as a Laker.

In the 2001 season, Harper missed 35 games due to injuries, and was only able to play in 6 games during the Lakers' playoff run. He announced his retirement at the end of the season.

While it cannot be said that any of his teams won because of Harper, he was the rare selfless player who was able to sacrifice his own statistics and minutes for the sake of the team.